Electrical-conductive rubbery composition and method of making same



Patented May 20, 1952 ELECTRICAL-CONDUCTIVE uncanny GOM- PQSITIQNANDMETHOD OF MAKING sane Joseph Hugh Macey, Akron, Ohio, assignor to The:B. F. Goodrich Company, New York, N. Y., a

corporationof New York No Drawing. Application'November 29, 1950,

Serial No. 198,246

'Thisinvention relates to a rubbery composition and pertains moreparticularly to an electricalconductive rubbery composition capable of'readily discharging to an electrical ground static electrical chargesdeveloped therein and the method of making same.

It is an object of this invention to provide an electrical-conductiverubbery composition adapted to readily discharge static electricalcharges 13 Claims. (Cl. ZED-4L5) such as acetylene black will decreasethe resistivity of the composition rather than increase it, contrary toall expectations.

Among the rubber-like materials which may be developed thereinminimizing, the possibility of employed in my invention are naturalrubber. the formation of a sufficient electrical potential such ascaoutchouc (which is a rubbery polymer between the rubbery compositionand an adjaof isoprene) and the like, or synthetic rubber, cent articleto cause sparking. such as the rubbery polymers of open-chained It isalso an object of this invention to provide conjugated dienes havingfrom four to eight caran electrical-conductive rubbery composition bonatoms exemplified by butadiene-IB; 2, 3-dicapable ofbeingreadilyiabric'ated'into numerous methyl butadiene-1,3; 1,4-dimethyl'butadieneconfigurations. 1,3 and the like,'or the rubbery copolymers ofAnother object of this invention is to provide these and similarconjugated dienes with each a Vulcanized y compos ti n which inother orwith copolymerizable monomeric mateher'entlypossessesa low electricalresistivity. rials containing a single ethylenic linkage. such Stillanother object of this'invention is to proas styrene, acrylonitrile,methyl acrylate, methyl vide "a convenient and economical method formethacrylate, ethyl acrylate, ethyl methacrylate, making a vulcanizedelectrical-conductive rub- Z-vinyl pyridine, or the rubbery polymersorco- 'bery composition. polymers of such dienes as chloroprene and theOther objects of this invention will be apparent like, or similarmaterials. Preferably the rubber- "from the description which follows.like material employed in my rubbery composi- The accumulation of staticelectrical charges tions is a vulcanizable rubbery conjugated diene onrubber articles often causes serious hazardous polymer. conditions toarise, in that the electrical poten- She polyethylenes employed in myinvention tia'l may become so great that a discharge of the 50 arepolymers of ethylene which are essentially electrical potential occursin the form of a spark straight-chain aliphatic hydrocarbons of varyingwhich may ignite inflammable and/ or explosive molecular weights and areproduced by the polymaterials in the immediate vicinity or causedismerization of ethylene in the presence of an comfort toapersoncomingin contact therewith. appropriate catalyst, such as benzoylperoxide, To m n mize t e a d of Sparking 'c y and under conditions ofintermediate to relathe instantaneous discharge of static electricaltively high temperatures and pressures. It is charges, rubbery bodies inwhich static electrical desirable that my rubbery composition comprisechar es ay p should ably be 'fablifrom 10 to 125 parts by weight of apolyethylene cated of a composition having a low electrical for every100 parts by weight of elastom-eric maresis ity allowing Staticelectrical charges 40 terial; however, to obtain optimum physical andformed therein to be harmlessly conducted to an chemical properties itis preferable that .my :r-ubelectrical ground before a sufficientaccumulation bery composition comprise from 20 to '75 parts of staticelectrical charges has occurred to cause by weight of a polyethylene forevery 100 parts a spark to formlbetween two or more bodies. In by weightof elastomeric material. Preferably addition, the combination ofelectrical conducthe polyethylene is a solid having a molecular tivitywith the physical and chemical properties weight of at least 6000,although liquid polyof rubber compositions may be desirable for otherethylenes having a molecular weight of as low as purposes. Since rubberycompositions ordinarily '200 or less may be employed in this invention.are inherently poor electrical conductors, special Electrical-conductivecarbon blacks which may compounding techniques are required in order beemployed in this invention .are carbon blacks 'to obtainelectrical-conductive rubber composihaving .a relatively .low electricalresistivity, preftions. Various electrical-conductive rubbery erably aspecific electrical resistance of approxicompositions such as thosecontaining acetylene mately ohm-cm. or less, such as acetylene blackhave been proposed but have .not been enblack, conductive channel blackand conductive 55 iurnaceblack. Itis desirable that from '40 to tirelysatisfactory, since large amounts of black parts by weight of anelectrical-conductive carbon black, preferably acetylene black, beincorporated in my rubbery composition for every 100 parts by weight ofelastomeric material, however, to obtain optimum physical and chemicalproperties, it is preferable that from 80 to 130 parts by weight of anelectrical-conductive carbon black be included in my rubbery compositionfor every 100 parts by weight of elastomeric or rubher-like material.Appropriate fillers, softeners, accelerators, age resisters, vulcanizingagents and reinforcing ingredients may also be included in my rubberycomposition to impart desired characteristics to the rubberycomposition.

The various components of my rubbery compositions may be compoundedtogether in any conventional manner, such as by milling the ingredientstogether on a roll mill or by mixing the ingredients together in aninternal mixer. Since polyethylene is compatible with the rubbermaterial at normal mixing temperatures its incorporation presents noproblem.

The following examples of rubbery compositions are cited merely toillustrate and fully teach my invention, however, it will be understoodthat I do not intend to limit the scope of this invention to theserecipes.

Example 1 Material: Parts by weight Natural rubber 100.0 Acetylene black80.0 Polyethylene 25.0 Benzothiazyl disulfide 1.4 Sulfur 2.0 Zinc OXide3.0

Syncera wax 2.0

Total 213.4

The ingredients were compounded together on a roll mill and vulcanizedin a mold at 292 for 15 minutes. The vulcanizate exhibited a specificresistance to the flow of an electrical current of less than 100 ohm-cm.at 20 C.

Example 2 Material: Parts by weight Rubbery butadiene-styrene copolymer(GR-S) (72% conversion) 100.0 Polyethylene 70.0 Acetylene black 100.0Sulfur 2.3 Zinc oxide 3.0 Syncera wax 2.0 Benzothiazyl disulfide 1.5

Total 278.8

The ingredients were compounded together and vulcanized as in Example 1and the vulcanizate possessed a specific resistance to the flow' of anelectrical current of less than 100-cm. at 20 C.

Example 3 Material: Parts by weight Rubbery polymer of chloroprene 100.0Acetylene black 60.0 Polyethylene 50.0 Zinc oxide 5.0 Sodium acetate 1.0Magnesium oxide 10.0 Syncera wax 2.0

Total 228.0

4 The ingredients were compounded together and vulcanized as in Example1 and the vulcanizate exhibited a specific resistance to the flow of anelectrical current of less than ohm-cm. at 20 C.

Example 4 Material: Parts by weight Rubbery butadiene-acrylonitrilecopolymer (2:1) (Hycar OR-25) 100.0 Polyethylene 25.0 Acetylene black120.0 Zinc oxide 8.0 Benzothiazyl disulfide 2.0 Sulfur 2.0Tributoxyethyl phosphate 40.0

Total 297.0

The ingredients were compounded together on a roll mill and vulcanizedas in Example 1 and the vulcanizate possessed a specific resistance tothe flow of an electrical current of less than 100 ohm-cm. at 20 C.

Rubbery compositions within the purview of this invention inherentlypossess a low electrical resistivity exhibiting a specific resistance tothe fiow of an electrical current of 100 ohm-cm. or less at 20 C.Conventional electrical-conductive rubbery compositions are much lesssatisfactory as electrical-conductive rubbery materials, since theyexhibit a much higher specific resistance to the fiow of an electricalcurrent than do my rubbery compositions. For example, the rubberycomposition set forth in Example 4 exhibited a specific resistance tothe flow of an electrical current of less than 100 ohm-cm. at 20 C.while a rubbery composition identical to that of Example 4 except thatno polyethylene was present exhibited a specific resistance of 1000ohm-cm. at 20 C. Furthermore, the electrical conductivity of my rubberycompositions does not decrease upon flexure while a rubbery compositionidentical to the rubbery composition of Example 4 except that nopolyethylene was included therein exhibited a specific resistance to thefiow of an electrical current after fiexure'of about 40,000 or moreohm-cm. at 20 C.

My electrical-conductive rubbery compositions are particularly useful inrubbery articles utilized under conditions where the formation of staticelectrical charges are likely to occur and have proven extremely usefulin articles such as gasoline-hose nozzles, anaesthesia masks, rubberhose, floor coverings, industrial belts, shoe soles, and the like.

It is clear that obvious modifications and variations of my inventionmay be made without departing from the spirit and scope of thisinvention as defined in the appended claims.

I claim:

1. A vulcanizable rubbery composition comprising a vulcanizable rubberyconjugated diene polymer, from 10 to parts by weight of polyethylene forevery 100 parts by weight of said rubbery conjugated diene polymer, andfrom 40 to parts by weight of an electrical-conductive carbon black forevery 100 parts by Weight of said rubbery conjugated diene polymer.

2. A vulcanizable electrical-conductive rubbery composition comprising avulcanizable rubbery conjugated diene polymer, from 20 to 75 parts byweight of polyethylene for every 100 parts by weight of said rubberyconjugated diene polymer, and from 40 to 150 parts by weight of anelectrical-conductive carbon black for every 100 parts by weight of saidrubbery conjugated diene polymer.

3. A vulcanizable electrical-conductive rubbery composition comprising avulcanizable rubbery conjugated diene polymer, from to 125 parts byweight of polyethylene for every 100 parts by weight of said rubberyconjugated diene polymer, and from 80 to 130 parts by weight of anelectrical-conductive carbon black for every 100 parts by weight of saidrubbery conjugated diene polymer.

4. A vulcanizable electrical conductive rubbery composition comprising avulcanizable rubbery conjugated diene polymer, from to '75 parts byweight of polyethylene for every 100 parts by weight of said rubberyconjugated diene polymer, and from 80 to 130 parts by weight of anelectrical-conductive carbon black for every 100 parts by weight of saidrubbery conjugated diene polymer.

5. An electrical-conductive rubbery composition comprising a vulcanizedrubbery conjugated diene polymer, from 10 to 125 parts by weight ofpolyethylene for every 100 parts by weight of said rubbery conjugateddiene polymer, and from 40 to 150 parts by weight of anelectricalconductive carbon black for every 100 parts by Weight of saidrubbery conjugated diene polymer.

6. An electrical-conductive rubbery composition comprising a vulcanizedrubbery conjugated diene polymer, from 20 to '75 parts by weight ofpolyethylene for every 100 parts by weight of said rubbery conjugateddiene polymer, and from 40 to 150 parts by weight of anelectrical-conductive carbon black for every 100 parts by weight of saidrubbery conjugated diene polymer.

'7. An electrical-conductive rubbery composition comprising a vulcanizedrubbery conjugated diene polymer, from 10 to 125 parts by weight ofpolyethylene for every 100 parts by weight of said rubbery conjugateddiene polymer, and from 80 to 130 parts by Weight of anelectrical-conductive carbon black for every 100 parts by weight of saidrubbery conjugated diene polymer.

8. An electrical-conductive rubbery composition comprising a vulcanizedrubbery conjugated diene polymer, from 20 to parts by weight ofpolyethylene for every 100 parts by weight of said rubbery conjugateddiene polymer, and from to 130 parts by weight of anelectrical-conductive carbon black for every parts by weight of saidrubbery conjugated diene polymer.

9. An electrical-conductive rubbery composition comprising a vulcanizedrubbery conjugated diene polymer, from 20 to '75 parts by weight ofpolyethylene for every 100 parts by weight of said rubbery conjugateddiene polymer, and from 6 80 to 130 parts by weight of an acetyleneblack for every 100 parts by weight of said rubbery conjugated dienepolymer.

10. A rubber-like composition comprising a rubbery polymer ofchloroprene, from 10 to parts by weight of polyethylene for every 100parts by weight of said rubbery polymer of chloroprene, and from 40 to150 parts by weight of an electrical-conductive carbon black for every100 parts by weight of said rubbery polymer of chloroprene.

11. The method of making an electrical-conductive rubberycompositionwhich comprises blending a vulcanizable rubbery conjugated diene polymerand from 10 to 125 parts by weight of polyethylene for every 100 partsby weight of said rubbery conjugated diene polymer together, dispersingfrom 80 to parts by weight for every 100 parts by weight of said rubberyconjugated diene polymer of an electrical-conductive carbon black intosaid blend, and vulcanizing the rubbery composition.

12. The method of making an electrical-con.- ductive rubbery compositionwhich comprises blending together a vulcanizable rubbery conjugateddiene polymer and from 20 to 75 parts by weight of polyethylene forevery 100 parts by Weight of said rubbery conjugated diene polymer,dispersing into the resulting blend from 40 to parts by weight of anelectrical-conductive carbon black for every 100 parts by weight of saidrubbery conjugated diene polymer, and vu1- canizing the rubberycomposition.

13. The method of making an electrical-conductive rubbery compositionwhich comprises blending together a vulcanizable rubbery conjugateddiene polymer and from 20 to '75 parts by weight of polyethylene forevery 100 parts by weight of said rubbery conjugated diene polymer,dispersing into the resulting blend from 80 to 130 parts by weight of anelectrical-conductive carbon black for every 100 parts by weight of saidrubbery conjugated diene polymer, and vulcanizing the rubberycomposition.

JOSEPH HUGH MACEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,377,153 Hunter et a1 May 29,1945 2,455,910 Alderson Dec. 14, 1948 FOREIGN PATENTS Number CountryDate 602,677 Great Britain June 1, 1948

5. AN ELECTRICAL-CONDUCTIVE RUBBERY COMPOSITION COMPRISING A VULCANIZEDRUBBERY CONJUGATED DIENE POLYMER, FROM 10 TO 125 PARTS BY WEIGHT OFPOLYETHYLENE FOR EVERY 100 PARTS BY WEIGHT OF SAID RUBBERY CONJUGATEDDIENE POLYMER, AND FROM 40 TO 150 PARTS BY WEIGHT OF ANELECTRICALCONDUCTIVE CARBON BLACK FOR EVERY 100 PARTS BY WEIGHT OF SAIDRUBBERY CONJUGATED DIENE POLYMER.